This process permits the preparation of unsaturated esters and halides containing straight chained hydrocarbon groups of a predetermined chain length which are valuable intermediates from which the corresponding straight chained alcohols, diols and diesters can be obtained by means of hydrogenation or saponification.
1. Field of the Invention
The present application relates to a process for preparing olefins by metathesis of two different olefins. The term metathesis, as used in the present specification, is meant to connote the interaction of two structurally different olefins. In particular, the present invention pertains to a process for preparing olefins by metathesis of at least two different olefins, only one of which comprises at least one functional group.
2. Description of the Prior Art
Several examples of this type of reaction are known in the prior art literature. For example, in an article of P. B. Van Dam, M.C. Mittelmeyer, and C. Boelhouwer in J.C.S. Chem. Comm. 1972, 1221, a metathesis between methyl oleate and hexene-3 in the presence of a catalyst, containing tungsten hexachloride and tetramethyl-tin, is disclosed. The French Pat. No. 2,252,314 also pertains to the metathesis of an olefin and an olefin comprising a functional group in the presence of a catalyst, which is a combination of a component selected from the group of tungsten compounds, molybdenum compounds, and rhenium compounds and an organic aluminum compound, containing at least one carbon-aluminum-bond.
One of the major objects of the metathesis-reaction according to the present invention resides in the preparation of straight-chained unsaturated esters or diesters which are valuable intermediates, which can be transformed into the corresponding straight-chained saturated alcohols or diols by means of complete hydrogenation or saponification or into the corresponding saturated monoesters or diesters by means of moderate hydrogenation. Such alcohols, containing between about 12 and 18 carbon atoms, are known to possess excellent detergent activities and to be totally biologically decomposable. The saturated diesters are used as comonomers in polycondensation reactions with, for example, diamines or diols. These straight-chained, unsaturated esters can be obtained directly by metathesis of two different olefins, one of which comprises at least one appropriate ester group, or indirectly by methathesis of two different olefins, one of which comprises at least one group which subsequently can readily be replaced by an ester group.
In the preparation of acyclic olefins comprising at least one functional group, it is important that the chain-length of the straight-chained portions of the resulting molecules can be adjusted to a desired value, according to the intended use of the products. Thus, in the beforementioned particular case of preparing products which are adapted for detergent purposes, it is important that the products comprise hydrocarbon groups of a sufficient chain-length, that is a chain-length equivalent to from about 12 to about 18 carbon atoms. Moreover in the case of products to be used in polycondensation reactions, it is important that the products have a well defined chain length to ensure stable thermomechanical and mechanical properties to the polymers. It is difficult to obtain a desired chain-length, if an olefin comprising a functional group and a straight-chained olefin are used as starting materials. Such olefins, which must contain a relatively high number of carbon atoms, are not readily available in amounts necessary for industrial production. On the other hand, straight-chained olefins may undergo isomerization at the double bound during the metathesis and this would reduce the selectivity of the reaction in forming compounds containing straight-chained hydrocarbon groups.